When somebody tells you they’ve done an engine swap in their 1970 Plymouth Road Runner, the first thing that usually comes to mind is a big block or modern Hemi transplant. The last thing you’d ever expect is a Detroit Diesel 3-53. Yes, you heard that right. Jon Shaw, the owner of this Road Runner decided to go completely against the grain and opted for something totally different.

Jon explains that he picked up the originally 383 4 speed powered B-Body back in 1986 for $300 and then went about installing a 159ci (2.6L) Detroit Diesel 3-53 inline-three engine, which is connected to a factory A-833 four-speed transmission. The engine runs on a 50/50 mix of diesel and cooling oil. While the engine isn’t exactly a rocket with a measly 101 horsepower and 205 ft-lbs of torque; it does give great fuel economy numbers of 25 mpg!

Jon says he’s a fan of the three cylinder’s sound and plans to add a turbo and swap in bigger fuel injectors; an upgrade he estimates will double the engine’s power, “I’ve put almost 12,000 miles on it with no heat problems. I don’t even have a fan on it.”
 
As you can see in the below video, the Road Runner isn’t exactly quick by any means, but it certainly does have a unique engine note! While the big B-Body Plymouth might not win any stoplight drags, this very unique oddball swap is certain to draw a crowd at any car show or meet.